1. Field of the Invention
The present invention relates to branched polymers, their properties, compositions and uses thereof.
2. Description of Related Art
There is a desire to extend the performance of polymers beyond what is currently known. In many applications polymers that exhibit low viscosity while maintaining benefits of a higher molecular weight are needed. Such polymers could be used in spraying, pumping, and mixing applications that currently are limited by high viscosity. Likewise, there is a demand for polymers that offer better processability (like blendability, mixability, pumpability, and/or extrudability) to enable entirely new formulations that cannot otherwise be created. Examples of limitations may include high equipment torque, motor failure, and/or product inhomogeneity. One approach to this problem is to synthesize branched polymer variants.
Branching agents are compounds that have the functionality to link one monomer and/or polymer chain to another monomer and/or polymer chain, resulting in polymers that are non-linear polymers, or partially crosslinked polymers. The non-linear and/or partially crosslinked polymers may contain linear polymer portion(s), and combinations thereof.
Among other factors, the resulting polymer properties can depend on the selected monomer(s), branching agent(s), their addition levels, resulting polymer chain densities, and polymerization solvent (or solvent blend), if used. Low addition levels of these branching agents can give rise to branched polymer behavior, meaning that the polymer does not exhibit properties typical of polymers made without the branching agent. Branched polymers may exhibit a lower viscosity than linear polymers of equal molecular weight made without the branching agent, an effect attributed in part to fewer polymer chain entanglement arising from the branched polymer architecture. Because they lack extensive covalent bonds between polymer chains (which is achieved at high branching agent addition levels), a branched polymer exhibits a solubility in the same solvents that solubilize the analogous polymer of equal molecular weight but synthesized without the branching agent(s). As just mentioned, with further increases in the branching agent(s), the resulting polymer can display networked hydrogel behavior, which may include elastic properties such as increased elongational viscosity and/or higher strengths. At high addition levels crosslinked polymers may be created, becoming very rigid or glassy, such as phenol-formaldehyde materials.
It is known to those skilled in the art that polymers having the same chemical composition but having different branching may have different properties. See, for general background, F. W. Billmeyer, Textbook of Polymer Science, 3rd Ed., John Wiley and Sons, New York, 1984; P. J. Flory, Principles of Polymer Chemistry, Cornell University Press, 1953; and C. Tanford, Physical Chemistry of Macromolecules, John Wiley and Sons, New York, 1961.
Related disclosures include WO 2007/096400, WO 2008/032342, and U.S. Pat. Nos. 5,300,606; 5,338,815; 5,534,174 and 5,788,950.
Disclosures of branched polymers, especially poly(N-vinyl-2-pyrrolidone), are provided in U.S. Pat. Nos. 5,082,910; 5,159,034; and 6,294,064. The '910 and '034 inventions provide processes for preparing linear polymers of high molecular weight, as contrasted to branched polymers of low molecular weight. Also known are poly(N-vinyl-2-pyrrolidone)-b-polyester, as disclosed on U.S. patent application 2008/0262105. An additional description of branched polymers includes co-pending U.S. patent application Ser. No. 12/984,926.
Related disclosure also includes international patent application PCT/US11/20208, which is hereby incorporated in its entirety by reference. That application provides polymers resulting from the polymerization of at least one reactive vinyl monomer moiety and a multifunctional N-vinyl formamide crosslinking moiety.
Also related are the following U.S. Pat. Nos. 4,774,285; 4,952,558; 5,202,112; 5,334,375; 5,385,729; 5,534,174; and 5,569,725; 6,197,908; 6,252,026; 7,135,598; 7,579,403; 7,833,585; 7,498,395; and U.S. patent applications 2006/0116492 and 2010/00144958; and international application WO 1992/015628 and 2010/149957